The invention relates to removable end-closure structure for sealed application to the end of a pipe of given outside diameter, to enable hydrostatic pressure-testing of the pipe.
For certain end uses, pipe specifications require an ability to withstand relatively high internal hydrostatic pressures, for example, 500 psi of water for a fabricated pipe unit of 42-inch outer diameter. Such capability must be demonstrated before the assembled pipe unit leaves the premises of the pipe fabricator, and it is important that the hydrostatic-pressure capability be demonstrable, however complex the pipe section; for longitudinally seamed pipe, the maximum length of seam must be subject to the test, as well as any and all circumferentially seamed connections of bent and straight components of the particular fabricated-pipe unit.
For irregularly shaped assemblies, past practice has involved one of two techniques, to removably close each open end of a particular pipe assembly, prior to shipment. According to one technique, anchor fitments are welded to the outer surface of the pipe near the end to be closed, and a closure plate or head is welded to the pipe end, with referencing connection to the anchor fitments; of course, after the test, the welded connections must be severed, and refinishing is required if cosmetic appearance has any importance. According to the other technique, an elastomeric plug (of length approximating the diameter to be closed) is inserted within the bore of the pipe end to be closed, and the plug is expanded, by internal application of hydraulic pressure, into tightly sealed axial and circumferential engagement with the bore.
Both of these existing techniques have their distinct limitations. Each closure which involves welding necessarily also involves custom attention to establishment of the anchorage and of the closure, as well as to costly disassembly of the closure and cosmetic restoration. Further, it is a fact of life that large-diameter pipe is specified for its outer diameter, the inner diameter being not held to strict tolerance, so that any plug for a given pipe diameter presents a real problem of adaptability. Also, the problem of plug fitment is particularly severe for the case of large-diameter pipe which is the product of longitudinally welding rolled ends of sheet material. Still further, use of the plug technique requires such excessive insertion length as to preclude application to elbow ends and, to the extent of the insertion length, a longitudinal seam will not have been exposed to hydraulic fluid under pressure.